Manganese aluminum alloy for deoxidizing steel



United States Patent 3,119,683 MANGANESE ALUMHJUM ALLOY FOR DEUXIDIZINGSTEEL William Rodgers, Shaker Heights, and Andrew G. Forrest, PepperPike, Ohio, assignors to Republic Steel glorporation, Cleveland, Ohio, acorporation of New ersey N0 Drawing. Filed Sept. 13, 1960, Ser. No.55,727 5 Claims. (Cl. 75129) This invention relates to the manufactureof steel. More particularly, it relates to an improvement in the surfacequality and internal cleanliness of steel effected by control of thenon-metallic inclusions therein.

In the production of high quality steel, the amount and type ofnon-metallic inclusions is of importance with respect to the aging andother properties of the steel. For many purposes, it is necessary thatthe silicon content of the steel be as low as possible and that thesteel be substantially free of silicate inclusions. Particularly in deepdrawing steels, these inclusions appear in and near the surface of thefinished products. This detracts from the surface appearance andsmoothness of the finished product and is highly undesirable.

In the basic open-hearth furnace operation, for example, one of the mainsources of silicate inclusions is from the refractories used in thefurnace spout, ladle, and pouring nozzle. Various methods have beenpracticed for producing a clean steel, based mainly on the reduction ofthe oxygen content of the steel by maintaining a reducing or deoxidizingslag. Also, the use of purer raw materials has been contemplated.Moreover, final deoxidizers, such as aluminum, silicon, etc., have beenused to remove the oxygen from the iron oxide dissolved in the steel.

Most of these methods merely substitute one type of inclusion foranother for the purpose of producing a less objectionable type ofinclusion, that is one which has a more favorable effect on the agingproperties of the steel. For certain types of steel, such asdeep-drawing steels or steels which are heavily deformed in the courseof fabrication, is is particularly desirable that the steel besubstantially free of silicate inclusions, regardless of whether suchinclusions result from the original charge, the flux, the deoxidizers,or from the refractories with which the steel comes in contact.

With regard to any unavoidable inclusions, it is desirable that thesenot be present in or near the surface. Therefore, in ingot formation,while it is most desirable to have the inclusions rise to the top of themolten ingot, any inclusions which do not so rise are located desirablynear the center of the ingot. This location of any unavoidableinclusions favors fewer inclusions at or near the surface upon deepdrawing of the resultant solid ingot.

It has now been found that the amount of silicate inclusion in steelscan be decreased most effectively and the location of such inclusions beimproved so as to produce a substantially clean steel by the use of adeoxidizing alloy consisting essentially of 50-75% by weight of manganese and 50-25% by weight of aluminum. This deoxidizing alloyadvantageously is added to the steel in the ladle. The amount of suchalloy to be added for this purpose is advantageously in the range of -20pounds, preferably 12-18 pounds of alloy per ton of the total charge.Advantageously, the silicon content of the charge materials and thedeoxidizers are kept as low as possible and contact with silicaterefractories is kept to a practical minimum. Silicon contentadvantageously is kept below 0.01% by weight.

In cases where the silicon or silicate contamination is very small, thealloy can be added immediately after the steel is poured into the mold.In such cases, less time is required for reaction of the small amount ofcontam- 3,119,688 Patented Jan. 28, 1964 "ice inant and very often thiscan be effected before the steel has solidified. However, ladle additiongenerally is preferred.

While applicant does not wish to be restricted to any theory, it isbelieved that the intimate contact of manganese and aluminum in thealloy favors simultaneous and intimate reaction with the silicates toproduce lower melting mixed silicates than are produced by theindividual metals. The individual si'l-icates having higher meltingpoints precipitate nearer the outer surface of the ingot whereas thelower melting mixed silicate stays molten longer, giving it more time torise to the top of the ingot or at least to migrate to the center partof the ingot.

The invention is illustrated best by the following examples which areintended to be merely illustrative of various methods of practicing theinvention and are not to be regarded in any way as limiting the scope ofthe invention. Parts and percentages, here and throughout thespecification, are parts and percentages by weight unless otherwiseindicated.

EXAMPLE I Various steel heatings are prepared in a basic openhearthfurnace, according to normal practice, having the preliminary analysesindicated in the table below. The first two of these heatings arecontrols, controls A and B using steels which are killed with aferro-manganese alloy and aluminum bar. In heatings I-V amanganese-aluminum alloy is added in the amounts indicated in the table.In each case the metal or alloy used to kill the steel is added to thesteel in the ladle, and 200 pounds of cryolite also is added to theladle. In each case also the silicon content is less than 0.01% byweight in both analyses. The resultant ladle analyses are given in thetable.

Table 0 ontrol Heatings Preliminary Analyses of Steel A B I II III IV VCarbon 1. 05 1. 08 1. 09 1. 20 1. 50 49 .74 Manganese .14 .11 .14 10 .21Phosphorus. 031 .027 035 030 .036 .02 025 Sulfur 042 04 047 041 042 048045 Tons of Steel 227 204 222 203. 5 222 222 240. 5 Mil-Al alloy (Lbs)2, 800 3,600 3, 600 3, 600 3, G00 Fe-Mn alloy h (Lbs) 2,100 1, 800

Manganese- 32 3O .24 .34 .31 .37 .34 Phosphorus .009 .010 .010 010 006006 .008 Sulfur 027 .032 029 .029 .030 025 .034 Aluminum .09 .06 .025 06.04 09 08 An alloy of 59.76% Mn and 39.99% Aladded to the ladle. Alloyof Mn (medium carbonapprox. 1%)added to the ladle. Aluminum bars-addedto the ladle.

In each case the various products are processed through the bloomingmill, the hot mill, the cold mill, and tested by pickling and etching.In each case the steels which are killed with the alloy show, uponmicroscopic examination, to be much cleaner than the two controls. Thesesteels have excellent surface appearance and cleanliness in comparisonwith the controls. The deep etch test shows these alloy-killed steels tobe sound and free from sub-surface inclusions, much more so than thecontrol steels. In the blooming mill, hot mill, and cold mill tests,these alloykilled steels have excellent rolling and surface qualitiesand show uniformity of hardness, ductility, grain size, and grain shape.In the pickling test, these alloy-killed steels have improved surfaces.

While the preferred proportions of metals in the alloy are approximately60% manganese and 40% aluminum, as used in the above example, improvedresults also are obtained'when the manganese content varies from 50% to75% and the aluminum content from 50% to 25% in the alloy. While theproportion of alloy can vary from approximately pounds to pounds per tonof steel with improved results, preferably the amount is about 12-18pounds of alloy per ton of steel. The alloy can be added as shot,buttons, bars, or small ingots.

Certain featuresof this invention have been described in detail withrespect to various embodiments thereof. However, it will, of course, beapparent that other modifications can be made within the spirit andscope of this invention, and it is not intended to limit the inventionto the exact details shown above except insofar as they are defined inthe following claims.

The invention claimed is:

1. In a process for producing a deep-drawing steel, the step comprisingthe addition to said steel of a manganesealuminum alloy subsequent totapping of the furnace and while said steel is still in a molten state,saidalloy consisting essentially of at least about 50 percent by weightmanganese and percent by weight of aluminum, and no more than about 75percent by weight of manganese and percent by weight of aluminum, saidsteel and said alloy each containing prior to said addition less than0.01 percent by weight of silicon, and said alloy being added in a format least as large as shot and in an amount of at least a about 10 poundsand no more than about 20 pounds per ton of steel.

2. A process of claim 1 in-which said alloy is added to the steel whilesaid steel is in the ladle.

3. A process of claim 1 in which said alloy is added immediately afterthe steel is poured into the ladle.

4. A process of claim 1 in which said alloy consists essentially ofabout parts by weight of manganeseancl 40 parts by weight of aluminum.

5. A process of claim 1 in which said alloy consists essentially ofabout 60 parts by weight of manganese and 40 parts by weight ofaluminum, and said alloy is added in an amount of approximately 12-18pounds per ton of steel.

References Cited in the file of this patent UNITED STATES PATENTS501,233 Richards et a1 July 11, 1893 1,744,418 Smith Jan. 21, 19302,767,084 Chandler Oct. 16, 1956 FOREIGN PATENTS 144,584 Germany July 2,1902 OTHER REFERENCES The Making, Shaping and Treating of Steel, 7thEdition, United States Steel, 1958, p. 328.

1. IN A PROCESS FOR PRODUCING A DEEP-DRAWING STEEL, THE STEP COMPRISINGTHE ADDITION TO SAID STEEL OF A MANGANESEALUMINUM ALLOY SUBSEQUENT TOTAPPING OF THE FURNACE AND WHILE SAID STEEL IS STILL IN A MOLTEN STATE,SAID ALLOY CONSISTING ESSENTIALLY OF AT LEAST ABOUT 50 PERCENT BY WEIGHTMANGANESE AND 25 PERCENT BY WEIGHT OF ALUMINUM, AND NO MORE THAN ABOUT75 PERCENT BY WEIGHT OF MANGANESE AND 50 PERCENT BY WEIGHT OF ALUMINUM,SAID STEEL AND SAID ALLOY EACH CONTAINING PRIOR TO SAID ADDITION LESSTHAN 0.01 PERCENT BY WEIGHT OF SILICON, AND SAID ALLOY BEING ADDED IN AFORM AT LEAST AS LARGE AS SHOT AND IN AN AMOUNT OF AT LEAST ABOUT 10POUNDS AND NO MORE THAN ABOUT 20 POUNDS PER TON OF STEEL.